[1] US Dept Hlth & Human Serv, Hlth Resources & Serv Adm, Maternal & Child Hlth Bur, Rockville, MD USA
[2] Natl Ctr Hlth Stat, Cts Dis Control & Prevent, US Dept Hlth & Human Serv, Hyattsville, MD USA
[3] US Census Bur, Demog Directorate, Survey Operat Econ & Stat Adm, Suitland, MD USA
[4] Johns Hopkins Bloomberg Sch Publ Hlth, Child & Adolescent Hlth Measurement Initiat, Baltimore, MD USA
[5] Hlth Resources & Serv Adm, Maternal & Child Hlth Bur, Div Epidemiol, Off Epidemiol & Res, 5600 Fishers Lane,Room 18N122, Rockville, MD 20857 USA